A friction damper with a housing including a cavity. The damper includes a first member disposed in the cavity and movable in the cavity; a second member disposed in the cavity; an intermediate member between the first and second members, the first member being in frictional engagement with the intermediate...http://www.google.fr/patents/US7243764?utm_source=gb-gplus-shareBrevet US7243764 - Magnetically actuated friction damper
